Commerical high-volume microwave systems require highly-integrated circuits in order to make production of the system practical. The use of monolithic microwave integrated circuits (MMIC's) is critical to achieving this goal. For the past 30 years, microwave integrated circuits (MIC's) have relied heavily upon thin film technology for patterning of conduce, resistive, and insulating films on a ceramic substrate. The films are either deposited selectively as the circuit pattern or applied as an entire film and then masked and selectively etched to the desired circuit patterns. Thus, with the trend toward Ku-band communication systems, the devices have incorporated discrete capacitors, resulting in MIC's with a large number of discrete components. As a specific example, a MIC Ku-band upconverter fabricated using thin film technology includes on the order of 80 discrete components assembled with the substrate. The necessity of including these discrete capacitors and integrated circuits results in large, relatively heavy devices which are labor intensive, considering the number of discrete components which must be added after the processing of the substrate itself. Looking again at the Ku-band upconverter, the area required is approximately 4700 mm.sup.2.
In addition to the large devices, thin film processing, while providing a great deal of precision in patterning, has several other disadvantages. Among these are the fact that deposited or sputtered conductor material is wasted by coating the inside of a vacuum chamber (i.e., a significant amount of gold is wasted), the ability to produce thick layers (greater than 0.5 mil) is limited, processing equipment is costly and cleanliness is critical so that expensive environmentally controlled facilities are required.
Thick film technology is well known for production of integrated circuit packaging and discrete components. The techniques and equipment required for thick film technology are significantly less stringent and less expensive than those for thin film processing. Further, thick film components can provide capacitors capable of operating at Ku frequencies. Thus, a thick film capacitor can provide the same capacitance values as those of discrete capacitors used with thin film processed substrates.
With the increase in the use of satellites for communications systems, the need is clear for reduced size and weight of components. It would, therefore, be desirable to provide an assembly which provides reduced size and weight which is capable of meeting the low loss requirements of microwave circuits. The process and devices of the present invention are directed toward attaining such a goal.